Switch with bridging cartridge fuse



- Jam 1964 E. G. E. JANSSON SWITCH WITH BRIDGING CARTRIDGE FUSE 2 Sheets-Sheet 1 Filed Nov. 14, 1960 INVEN'I OR ERIK GUNNAR EDVIN JANSSON TT ORNEY JAM. 6

Jan. 21, 1964 E. G. E. JANSSON 3,

SWITCH WITH BRIDGING CARTRIDGE FUSE I Filed Nov. 14, 1960 2 Sheets-Sheet 2 INVENTOR ERIK GUNNAR EDVIN JANSSON jq ATTORNEY United States Patent 3,118,990 SWITCH WITH BRIDGING CARTRIDGE FUSE Erik Gunnar Edvin Jansson, Stenvagen 5, Sorberge, Sweden Filed Nov. 14, 1960, Ser. No. 68,970 Claims priority, application Sweden Nov. 14, 1959 8 Claims. (Cl. 200-414) The present invention relates to electric switches having a frame, a bridge member which is movable with respect to the frame, and terminal members for incoming and outgoing conductors. More particularly, it relates to such switches of the kind set forth in which the bridge member is provided with contacts, herein termed movable contacts, which are adapted to cooperate with corresponding contacts carried by the frame, herein termed fixed contacts, and also with contact members provided on a number of electrical apparatus which are carried by the bridge member.

in recent years it has become common practice to apply the principle of construction set forth above, i.e., to mount electrical apparatus directly on the movable part of an electric switch. Such apparatus include, in the first instance, cartridge fuses, particularly so called grip fuses, but also current transformers, thermal current interrupters and the like. The said arrangement of the electrical apparatus involves several essential advantages, the most important one being a saving in space especially desired in switch cabinets and the like. Another important advantage is that conditions easily may be selected so that the apparatus carried by the movable bridge member are free from voltage when the switch occupies its open position, so that separating switches or the like can be dispensed with.

On the other hand, the said design entails certain difiiculties and inconveniences. Thus, the contact members of the apparatus in question are liable to become damaged through arcing in connection with the opening and closing movements of the bridge member of the switch. In such switches, in which the contact members of the apparatus carried by the bridge member have the shape of knives or blades which are inserted in fork-shaped contacts on the bridge member, it is known to let the latter contacts cooperate with corresponding fixed contact forks on the frame, whereby the knives or blades are protected from damages through the formation of electric arcs. The said protection is obtained, however, at the cost of another serious inconvenience, because, in an arrangement of that kind, on its way from the contact fork of the frame to the contact blade of the apparatus, the operating current obviously must pass two points of contact located in series. In principle this means a doubling of the total transition resistance in the circuit, and since switches of the kind in question normally carry heavy currents a correspondingly increased development of heat will occur which, of course, is undesired, for instance because of the increased risk of annealing of the material in the contacts. Another and often more serious inconvenience consists in that the forces required in connection with the opening of the switch for simultaneous separation of all the contacts become as a rule disproportionally high. The reason for this is that the total frictional surface is large and that in addition the contact pressure must be high, because otherwise the development of heat mentioned above would be higher than permissible.

It is a general object of the invention to provide a switch which combines the advantages found in both the abovementioned types of previously known switches without having the inconveniences found therein.

A special object of the invention is to protect the contacts of the apparatus carried by the bridge member from damages on account of electric arcs while making provision for a direct contact between the contacts of the apparatus and the contacts of the frame in the closed position of the circuit breaker or switch.

According to the main features of the invention the above objects and advantages have been realized by arranging the contacts of the bridge member and the contacts of the frame in such a manner with respect to each other and to the contact members of the electrical apparatus as to secure, in connection with the movement of the bridge member towards the frame for the purpose of closing the circuits controlled by the switch, at each pair of a fixed and a movable contact, a contact between the two said contacts and also a contact directly between the contact members of the appertaining apparatus and the fixed contact.

An embodiment of the invention will be described more closely below with reference to the accompanying drawmg.

FIGURE 1 is a perspective view of a switch in which the invention has been realized.

FIGURES 2a, 2b and 2c illustrate schematically the functioning in connection with the closing of the contacts of the switch according to FIGURE 1.

Reference numeral 1 denotes the frame of the switch, said frame being shaped as a bottom plate, and reference numeral 2 a bridge member which is movable in parallel with itself towards and away from the frame. Attached to the latter are a number of fork-shaped spring contacts 3, which are secured on a base 4 of insulating material and connected with terminal clips 5 which serve as terminal members for the incoming and outgoing conductors 6.

Mounted on the movable bridge member 2 are a number of electrical apparatus 7, which in the embodiment selected are assumed to consist of so called grip fuses. The fuse cartridges are provided at each end with a contact knife, or blade, 8 which is removably received in a corresponding fork contact 9 on the bridge member to permit replacement when desired. The latter contacts constitute the movable contacts of the switch. The movement of the bridge member in connection with the closing and the opening of the switch or circuit breaker is effected by means of a control rod 10 which is secured on a shaft 11 with a certain angular play. Rigidly secured on the shaft 11 is an arm 12 which by means of tooth segments is in engagement with a similar arm 13 on a shaft 14 parallel with the shaft 11. The free end of each arm 12 and 13 is provided with abutting surfaces adapted to cooperate with pins 15 and 16 projecting from the end surface of the bridge member. A strong tension spring 17 is biased to hold the said free ends of the arms 12 and 13 together. The details 12, 13 and 17 thus form together a toggle mechanism. A similar mechanism is provided at the opposite side of the circuit breaker.

In the embodiment of the invention illustrated on the drawing both the fork contacts on the frame and the fork contacts on the bridge member are composed of U- shaped blade springs placed in pairs opposite each other. Each such contact spring of the bridge member consists of a longer outer leg 9a and an inner shorter leg 91). The latter leg engages the contact blade 8, whereas the former is intended to cooperate with the contact springs of the frame. In the latter contact springs the outer legs 3a are .of essentially the same length as the inner ones 3b. A

helical compression spring 18 is biased to hold the legs apart. The reference numeral 19' designates a yoke member which limits the possibility of the outer legs 9a of moving away from each other. All the legs 3a, 3b of the fixed contact springs are substantially parallel with each other and with the contact blade 8, whereas the outer legs 9a of the movable contact springs converge in the direction from the frame 1.

The arrangement described above operates in the following manner. By means of the operating mechanism -47, the bridge member 2 may be rapidly moved towards or away from the frame 1, involving a closing and an opening of the circuits connected to the circuit breaker. FIGURE 2a shows a pair of fixed and movable contact forks in open position. In FIGURE 2b a closing movement has been initiated and the bridge member has moved so far towards the frame that the outer legs 3a of the contact springs of the latter have engaged the outer spring legs 9a of the bridge member. No direct contact has as yet been established between the contact blade 8 and the inner legs 3b of the contact springs of the frame. Such contact has been established in FIGURE 2c, which shows the switch in fully closed position.

It is immediately understood that, thanks to the arrangement of the fork contacts 3 and 9 described above, at opening as well as closing movements the electric arcs are formed between the outer contact spring blades 3a and 9a, so that the contact blade 8 is protected from the arc and from appertaining burns. When the contacts occupy the position corresponding to the closed position of the circuit breaker, the main portion of the working or operating current will pass directly from the fixed contact forks 3 to the contact blade 8 via contact surfaces which are always clean and undamaged. The rest of the current passes through the outer legs of the contact forks. As compared with such previously known arrangements in which the contact blades never get into direct contact with the fixed contact forks 3, the arrangement according to the invention has a considerably increased contact surface. Thanks to the converging shape of the spring legs 9a and through the provision of the compression springs 13 the contact pressure also becomes very high and increases successively as the fixed and movable contact forks penetrate deeper into one another. Further, an important advantage found in the arrangement according to the invention consists in that the strong magnetic fields set up in connection with a possible short-circuit will cancel each other because of the particular arrangement of the contact forks, so that no forces are set up which could move the electrical apparatus 7 away from their positions.

As already stated the embodiment of the invention described above and illustrated on the drawing is only intended to explain the principles of the invention. Thus the invention may be applied in switches of other types designed for another manner of operating movement of the bridge member and/or for circuit opening only at the one end of each apparatus carried by the bridge member. Yet, a double-sided interruption is preferred as a rule. As regards the shape and arrangement of the contacts there are also a greater number of modified constructions possible. Thus, it is, of course, possible to make the legs of the movable contact forks parallel, letting instead the outer legs of the fixed contact forks converge in the direction toward the contact blade. Furthermore, the legs may be given lengths different from those shown on the drawing. It must always be borne in mind, however, that in connection with the interruption of the current, portions of the fixed and of the movable contact forks must remain in contact with each other after the point of time when the contact blade 8 has been moved out of engagement with the fixed contact fork, so that the blade is protected from the formation of arcs.

I claim:

1. An electric switch comprising a frame, a bridge member, mechanism for guiding and moving said bridge member towards and away from said frame to respectively close and open said switch, a cartridge fuse removably carried by said bridge member, said cartridge fuse having two knife-shaped contact elements, a pair of fork-shaped contacts mounted on said bridge member and each such contact having spring arms spaced to receive and hold a knife-shaped contact of said cartridge fuse and being of such length as to cover only part of the contact surfaces of each contact element in the inserted position of the fuses, a pair of fork-shaped contacts mounted on said frame and adapted to be connected respectively to incoming and outgoing lines, said forkshaped frame contacts each having spring arms positioned and spaced to directly engage the exposed surfaces of a contact element of said fuse in the closed position of the switch, a pair of second contacts mounted on said frame and each electrically connected with a corresponding forkshaped frame contact, a pair of second contacts mounted on said bridge member each electrically connected with a corresponding fork-shaped bridge contact, the said second frame contacts being positioned to engage each a corresponding second bridge contact in the closed position of the switch, so that in said position one part of the load circuit will flow directly from said fork-shaped frame contacts to said cartridge fuses and the other part will fiow to the cartridge fuse in series with said second frame and bridge contacts.

2. A switch as claimed in claim 1, in which the forkshaped fuse holder contacts mounted on the bridge are constructed and sized in respect to the knife shaped contacts to engage substantially the entire length of the knifeshaped contact members of the cartridge fuses but only part of their width in the direction of switch closing.

3. A switch as claimed 1, wherein the fork-shaped contacts of the bridge member each consist of a number of blade springs arranged at opposite sides of the contact knife of each cartridge fuse, and said blade springs each have the shape of a U, the inner legs of each U-shaped contact spring being adapted to engage opposite faces of the contact knife of the cartridge fuse whereas the outer legs thereof constitute said second bridge contacts and are adapted to cooperate with corresponding second contacts of the frame.

4. A switch as claimed in claim 3, wherein said inner legs of the contact springs are shorter than the outer ones and preferably extend only across half of the contact knife measured from the edge remote from the frame.

5. A switch as claimed in claim 3, wherein the forkshaped contacts of the frame consist of the inner legs of U-shaped blade springs, and the outer legs of said U- shaped blade springs constitute the second frame contacts and are adapted to cooperate with corresponding second contacts on the bridge member.

6. A switch as claimed in claim 5, wherein, for the purpose of increasing the contact pressure, compression springs are provided between the two legs of each U- shaped blade spring on the frame.

7. A switch as claimed in claim 3, wherein, for the .purpose of increasing the contact pressure, some of the cooperating blade portions of the contact forks of the frame and of the contact forks of the bridge member are so disposed that on their engagement at least one of them is subjected to an elastic change of position.

8. A switch according to claim 3, wherein in that the legs of the contact springs of the frame are substantially parallel with the knife contact surfaces, whereas the outer legs of the contact springs of the bridge member converge in the direction from the frame.

Frank et a1. Sept. 6, 1938 Jackson et a1. July 7, 1942 

1. AN ELECTRIC SWITCH COMPRISING A FRAME, A BRIDGE MEMBER, MECHANISM FOR GUIDING AND MOVING SAID BRIDGE MEMBER TOWARDS AND AWAY FROM SAID FRAME TO RESPECTIVELY CLOSE AND OPEN SAID SWITCH, A CARTRIDGE FUSE REMOVABLY CARRIED BY SAID BRIDGE MEMBER, SAID CARTRIDGE FUSE HAVING TWO KNIFE-SHAPED CONTACT ELEMENTS, A PAIR OF FORK-SHAPED CONTACTS MOUNTED ON SAID BRIDGE MEMBER AND EACH SUCH CONTACT HAVING SPRING ARMS SPACED TO RECEIVE AND HOLD A KNIFE-SHAPED CONTACT OF SAID CARTRIDGE FUSE AND BEING OF SUCH LENGTH AS TO COVER ONLY PART OF THE CONTACT SURFACES OF EACH CONTACT ELEMENT IN THE INSERTED POSITION OF THE FUSES, A PAIR OF FORK-SHAPED CONTACTS MOUNTED ON SAID FRAME AND ADAPTED TO BE CONNECTED RESPECTIVELY TO INCOMING AND OUTGOING LINES, SAID FORKSHAPED FRAME CONTACTS EACH HAVING SPRING ARMS POSITIONED AND SPACED TO DIRECTLY ENGAGE THE EXPOSED SURFACES OF A CONTACT ELEMENT OF SAID FUSE IN THE CLOSED POSITION OF THE SWITCH, A PAIR OF SECOND CONTACTS MOUNTED ON SAID FRAME AND EACH ELECTRICALLY CONNECTED WITH A CORRESPONDING FORKSHAPED FRAME CONTACT, A PAIR OF SECOND CONTACTS MOUNTED ON SAID BRIDGE MEMBER EACH ELECTRICALLY CONNECTED WITH 